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Arun Isaac
Type devroom
Tree-diff for lisp source code
Starts on day 2 (2021-02-07) at 13:05 (Brussels time, UTC+1) in room Declarative minimalistic (duration 00:20)
Matrix room #declarative minimalistic:fosdem.org
Lisp has a wonderful minimal syntax that almost directly expresses the
abstract syntax tree. Yet, diff and other tooling operate on the unix
newline ending model. When lisp prides itself for its minimal
syntax---code is data---that is easy to parse, why can't we do better?
Traditional diff implementations, such as GNU Diff, treat files as a
flat list of lines. A tree-diff algorithm that can produce minimal and
semantically meaningful output is a surprisingly more difficult and
complex problem. In fact, for unordered trees, the problem is NP-hard.
In this talk, I will demonstrate a very early working prototype of an
S-expression diff program. The program can operate on two versions of
some lisp source code and extract a meaningful tree-diff. The program
aims to replace 'git diff' and related tools for lisp projects.